A series-compensated power transmission line typically incorporates a capacitor that is coupled in series with the power transmission line to compensate for the distributed series inductance presented by the power transmission line. The capacitive compensation is directed at optimizing power transmission capacity over the power transmission line. Also typically, a protection element such as a metal-oxide varistor (MOV) is coupled in parallel with the capacitor in order to prevent damage to the capacitor when a fault, such as a short-circuit for example, occurs on the power transmission line.
Unfortunately, the overall line impedance of the series-compensated power transmission line changes in a non-linear manner when the MOV transitions from a non-conducting state to a conducting state upon the occurrence of a fault. Additionally, the overall line impedance can vary in a somewhat unpredictable manner due to various factors such as the nature of the fault (short circuit, open circuit, bridged short across lines etc.), the severity of the fault, and the conduction characteristics of the MOV. Consequently, the use of a conventional fault locating system, which may be quite effective on a non-compensated power transmission line having a substantially consistent impedance characteristic, may turn out to be inadequate for identifying a fault location in a series-compensated power transmission line.
One traditional approach for addressing this issue involves the use of a different type of fault locating system that incorporates a deterministic procedure and takes into consideration the characteristics of the protection element (the MOV, for example) and various parameters associated with the faulty power transmission line. Such a procedure can include for example, various steps such as modeling the series compensated power transmission line, modeling the compensating capacitor, modeling the MOV, and monitoring the operational status of the MOV. Another traditional approach involves making an assumption of a faulty segment in a multi-segment power transmission system and executing a fault location procedure based on the assumption. Once a faulty segment is accurately identified, the exact location of the fault on this faulty segment has to be identified. Understandably, such traditional approaches can not only be complex and ambiguous but may also lead to imprecise results as a result of the assumptions being made.